They are indeed in defiance of the UN Security Council. The UN Security Council has demanded that they stop uranium enrichment. However, the Nuclear Proliferation Treaty states that all countries can pursue this technology if used for peaceful purposes. So as is very often the case, the UN Security Council members are ignoring the treaty that they are all a signature to.

But there are many countries in defiance of the UN Security Council. There is one country that has been in defiance of the UN Security Council for 38 years. Look up UN Security Council Resolution #242.

What do you think the UN should do about that one? Should they take action against the country that has been in defiance for 38 years before they do so against the country that has been in defiance for just a few hours? Or should they selectively ignore certain cases of defiance and cherry pick which ones they respond to?